Microcrystalline-Silicon-Oxide-Based N-Type Reflector Structure in Micromorph Tandem Solar Cells

Abstract

N-type microcrystalline silicon oxide thin films (n-𝜇c-SiO𝑥:H) have been deposited by VHF-PECVD (40 MHz) with reactant gas mixtures of CO2/SiH4 and H2. N-𝜇c-SiO𝑥 thin films exhibiting low refractive index value (n600nm∼2), and medium/high conductivity (≧10−9 S/cm) are suitable to be used as an “n-type reflector” in micromorph tandem solar cells. Transmission electron microscopy (TEM) results show that microstructures of n-𝜇c-SiO𝑥:H thin films contain nanocrystalline Si particles, which are randomly embedded in the a-SiO𝑥 matrix. This specific microstructure provides n-𝜇c-SiO𝑥:H thin films excellent optoelectronic properties; therefore, n-𝜇c-SiO𝑥:H thin films are appropriate candidates for “n-type reflector” structures in Si tandem solar cells.